Refrigerated canned doughs are generally compositions packaged in foil surfaced fiber containers having vent holes or other means to allow gas to escape therefrom (U.S. Pat. Nos. 1,811,772 and 2,478,618). As the dough is proofed in the container, carbon dioxide is generated from the leavening system which expands the dough in the container and drives out the oxygen. The expanded dough seals the container. An internal gas pressure is required to maintain the seal and to keep the oxygen out of the container. The gas pressure must remain after refrigeration to maintain the seal. Failure to maintain the pressure will cause the dough to spoil due to bacteriological action which can spoil the biscuits and, in some instances, cause excessive gas pressure to be generated sufficient to cause the containers to rupture. The dough must also retain sufficient leavening to allow the product to rise when baked.
The leavening systems used in refrigerated canned doughs must be specifically adapted to satisfy certain criteria. The leavening system must develop gas at a slow enough rate initially to allow for mixing and handling. If too much gas is released during mixing, not enough will remain for sealing of the container (proofing). If a large amount of gas is generated after mixing but before the dough is placed in the can, the dough can puff causing problems in putting the proper dough weight into the container. After proofing, the containers must retain the internal pressure. Some leavening systems have been known to not maintain the pressure within the container upon refrigeration. In some commercial establishments, up to 40% of the dough, i.e. that left after cutting, is recycled requiring control of the leavening. In essence, the leavening system must provide the right amount of gas at various times from mixing to final baking.
Sodium acid pyrophosphate (hereinafter SAPP) has been found to be especially well suited to the needs of preleavened packaged doughs and is widely used for that purpose. The addition of minor amounts of K.sup.+, Ca.sup.++, and Al.sup.+++ to the SAPP during manufacture permits the controlled retardation of the rate of reaction of the SAPP with the sodium bicarbonate in the baking system (Phosphorus, A.D.F. Toy, Comprehensive Inorganic Chemistry, Vol. 2, Chapter 20, 1973). A SAPP/bicarbonate leavening system fulfills the gas generation requirements for canned doughs.
However, the so-called "pyro" taste generally is considered objectionable.
The so-called "pyro" taste has been described as (1) a sensation that there is a coating on the roof of the mouth, (2) an astringent aftertaste and (3) a dry feeling that persists on the teeth for several minutes. It would be desirable to reduce the quantity of "pyro" used while maintaining the effective leavening properties which the pyrophosphate provides.
Also, the sodium acid pyrophosphate is only sufficiently slow for use in preparing refrigerated doughs if a mixing temperature about 18.degree.-21.degree. C. (65.degree.-70.degree. F.) is maintained in the mixing bowl. This is accomplished by pumping a refrigerated liquid through a jacketed mixing bowl. Avoidance of the requirement to maintain the mixing temperature within a limited range would be a desirable improvement. Also, recycle of the dough is not facilitated by this requirement.
Another well known leavening agent in the baking industry is sodium aluminum phosphate (hereafter SALP). It finds use in baking powders, self-rising mixes, preleavened pancake flours and mixes, prepared biscuit mixes, and prepared cake mixes. (See U.S. Pat. Nos. 2,550,491, 3,109,738, 3,041,177, 3,096,178).
Crystalline sodium aluminum phosphate (or SALP) was first disclosed in the U.S. Pat. No. 2,550,490, and an early baking powder composition incorporating SALP was disclosed in U.S. Pat. No. 2,550,491. U.S. Pat. No. 2,550,490 specifically discloses a SALP with a Na:Al:PO.sub.4 mole ratio of 1:3:8 (hereinafter 1:3:8 SALP). Since that time, several modifications of sodium aluminum phosphate have been developed which give different reactivities and performance characteristics. These include a dehydrated SALP, U.S. Pat. No. 2,957,750; a 3:3:8 SALP, U.S. Pat. No. 3,223,479; a 3:2:8 SALP U.S. Pat. No. 3,501,314; a 2:3:6 SALP, U.S. Pat. No. 3,574,536; an amorphous SALP, U.S. Pat. No. 2,995,421; a 3:3:9 SALP, U.S. Pat. No. 3,726,962 and a continuous crystallization of SALP, U.S. Pat. No. 3,311,448. The SALP's of commerce include a 1:3:8 SALP and 3:2:8 SALP.
Several proposals have been made in the past for improving the properties of sodium aluminum phosphate, particularly the flow characteristics and dust properties.
In U.S. Pat. No. 3,205,073, there is provided a potassium modified sodium aluminum acid phosphate having decreased hygroscopicity. This result is accomplished by modifying the original sodium aluminum phosphate molecule before, during or after preparation with the introduction of potassium. An improvement over U.S. Pat. No. 3,205,073 is U.S. Pat. No. 3,411,872, which attempts to improve the flow characteristics of the U.S. Pat. No. 3,205,073 potassium modified sodium aluminum phosphate by incorporating the potassium ions in a solvent suspension of an alkanol.
A further improvement in SALP is disclosed in U.S. Pat. No. 4,054,678 wherein a specific ratio of sodium and potassium is used to prepare a potassium modified SALP. The improved SALP product is characterized by increased density and reduced dusting properties.
A calcium treated SALP having improved handling characteristics and useful as a leavening agent in moist doughs and liquid batters is disclosed in U.S. Pat. No. 4,196,226. These products, as leavening acids, show improved holding and storage characteristics in moist doughs and liquid batters. Calcium sulfate has been added to SALP during manufacture as disclosed in U.S. Ser. No. 972,097, filed Dec. 21, 1978 now U.S. Pat. No. 4,260,591.
While 1:3:8 SALP is a well known leavening acid with no flavor problems, the use of 1:3:8 SALP in canned biscuits to replace the SAPP to overcome the flavor problem has not been successful. The leavening action of 1:3:8 SALP has been considered "too fast" for canned doughs. Under normal processing conditions, the use of 1:3:8 SALP leads to failure due to the bursting of cans caused by bacterial growth. Proper internal pressure cannot be maintained after refrigeration. SALP (slow acting) or 3:2:8 SALP, has been used in combination with SAPP at a 25/75 percent ratio of a refrigerated dough containing large amounts of solid shortening (U.S. Pat. No. 3,879,563). The biscuits are taught to be more of the homemade variety. Since the 3:2:8 SALP is slower acting than the other commercially available SALP, the 1:3:8 SALP, and since SAPP is known to be faster than either SALP, the combination of 3:2:8 SALP and SAPP does not provide teachings on how to overcome the problem of using 1:3:8 SALP in refrigerated canned doughs.
U.S. Pat. No. 2,957,750 discloses a dehydrated SALP. This patent teaches that the rate of reaction of 1:3:8 SALP and the solubility can be increased over that of commercial 1:3:8 SALP by removing from 3 to 4 waters of crystallization. Commercial 1:3:8 SALP of the formula EQU NaAl.sub.3 H.sub.14 (PO.sub.4).sub.8.4H.sub.2 O
is heated at 80.degree. to 200.degree. C. until the desired dehydration has taken place. This product would be of less utility in canned refrigerated doughs due to its faster leavening rate.
It is also known that storage of refrigerated doughs causes another problem, the appearance of glass-like crystals in the dough. These are caused by the crystallization of the phosphates. While the crystals are harmless as far as the product is concerned, the customer does not know or accept this so that complaints on this problem are frequent.
SALP, acidic has also been blended with up to 10% of an edible salt yielding trivalent aluminum such as aluminum sulfate as disclosed in U.S. Pat. No. 3,041,177, the disclosure of which is incorporated herein be reference. A blend containing about 93.5% SALP, acidic (prepared by process of U.S. Pat. No. 4,054,678) and 6.5% aluminum sulfate is available from Stauffer Chemical Company under the trademark BL-60.
Potassium sorbate can also be added as a dough conditioner. The potassium sorbate apparently decreases mixing time and apparently increases the storage stability of the dough product (see U.S. Pat. No. 3,556,798).
In U.S. Pat. No. 4,230,730 there is disclosed a new leavening acrd composition which can be used in leavening canned refrigerated dough comprising a potassium modified 1:3:8 sodium aluminum phosphate or the calcium modified derivatives thereof or mixtures thereof in combination with an alkali metal acid pyrophosphate. Unexpectedly, this leavening acid in combination with sodium bicarbonate produced gas at a rate slower than at least the fastest ingredient and, in many cases, slower than either leavening acid ingredient separately.